A great deal of interest has been focused on SSLSs, such as LEDs and lasers, and in particular, those that emit light in the blue and deep ultraviolet (UV) wavelengths. These devices may be capable of being incorporated into various applications, including solid-state lighting, biochemical detection, high-density data storage, and the like.
A modern SSLS such as an LED typically includes three major components: an electron supply layer (e.g., an n-type semiconductor layer), a hole supply layer (e.g., a p-type semiconductor layer), and a light generating structure formed between the electron supply layer and the hole supply layer. Nitride-based SSLSs typically have a relatively high defect concentration and operate at a high current density level. Failures of devices that include SSLSs generally occur as a result of these factors. These device failures that occur typically lead to the SSLSs forming a short-circuit path. High current flowing through a short-circuit path can cause propagating failures such as power supply or driver failures.
A high-power SSLS-based lamp assembly of LEDs is another type of SSLS device where failures can arise. Typically, high-power SSLS-based lamp assemblies often have multi-pixel structures where multiple small-area devices operate in parallel. In these small-area devices, the failure of a single pixel (i.e., an elementary SSLS) does not cause significant total power degradation, however, the related failures of the SSLS drivers and/or power supplies can cause the failure of the entire high-power lamp.
To address these failure issues associated with the various types of SSLSs, approaches have been deployed that rely on using circuits containing fuses connected in series with the SSLSs. Typically, these fuses are made from materials with low melting temperatures and/or with positive temperature coefficients of resistance. Thus, when a short-circuit failure occurs, the current through the SSLS increases as does the current through the fuse. This leads to the fuse melting and consequently disconnecting the defective device. However, the fuse melting is a relatively slow process before it can trigger the current off. As a result, sequential damage can still occur despite the protection provided by the fuse. Furthermore, the damage can be exacerbated by parasitic capacitances and inductors located between the fuse and the SSLS that may further slowdown the protection time and also lead to high current spikes caused by the short-circuit.
Electro-static discharge (ESD) protection is another type of protection measure that can be used with various types of SSLSs. One ESD protection approach involves using ESD protection elements connected in parallel with a SSLS. However, the parallel connection of the ESD protection elements are typically ineffective in protecting a system from short-circuit type failures because this type of protection does not remove the excessive voltage from being applied to the protected SSLS.